2003/05/16 by Jason X. Prochaska, J. X. Prochaska, Eric Gawiser +4 · 13 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/378945
published as Astrophys.J. 595 (2003) L9-L12 · 9 pages with 2 B&W figures. Submitted to ApJL (May 7, 2003)
arxiv created 2003/05/16 · openalex publication_date 2003/08/21 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
We discuss accurate metallicity measurements for 125 damped Lyα (DLA) systems at 0.5 < z < 5, including ≈50 new measurements from our recently published Echellette Spectrograph and Imager surveys. This data set is analyzed to determine the age-metallicity relation of neutral gas in the universe. Contrary to previous analyses, this sample shows statistically significant evolution in the cosmic mean metallicity. The best linear fit for metallicity evolution is -0.26 ± 0.07 dex per unit redshift. The DLA systems continue to maintain a floor in metallicity of ≈1/700 solar, independent of observational effects. This metallicity threshold limits the prevalence of primordial gas in high-redshift galaxies and stresses the correspondence between damped systems and star formation. Finally, we comment on an apparent "missing metals problem:" the mean metallicity of the damped systems is ≈10 times lower than the value expected from their inferred star formation history. This problem is evident in current theoretical treatments of galaxy formation and may indicate a serious flaw in our understanding of the interplay between star formation and metal enrichment.